<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body {
            font-size: 50px;
            margin: 0;
            padding: 0;
        }

        .box1 {
            width: 200px;
            height: 200px;
            background-color: #bfa;
            position: absolute;
            z-index: 1;
        }

        .box2 {
            width: 200px;
            height: 200px;
            background-color: rgba(255,0,0,.5);
            position: absolute;
            top: 50px;
            left: 50px;
            z-index: 2;
        }
        .box3 {
            width: 200px;
            height: 200px;
            background-color: yellowgreen;
            position: absolute;
            top: 100px;
            left: 100px;

        }
        .box4{
            width: 100px;
            height: 100px;
            background-color: orange;
            position: absolute;
            z-index: 3;
        }

    </style>
</head>
<body>
<div class="box1">1
</div>
<div class="box2">2</div>

<div class="box3">3
<div class="box4">4</div>
</div>


</body>
</html>
